The present invention relates generally to internal combustion engines, and, more particularly, to a method and apparatus for treating blow-by gases found in the crankcase of an internal combustion engine.
In internal combustion engines, including diesel and gasoline engines, a fuel and air mixture is combusted in combustion cylinders. A reciprocating piston in the combustion cylinder moves between top dead center and bottom dead center positions, compressing the fuel and air mixture as the cylinder moves towards the top dead center position and capturing energy released during combustion as the piston moves toward the bottom dead center position.
Combustion in the cylinder releases energy and generates combustion products and by-products, most of which are exhausted from the cylinder to an exhaust system of the engine during the exhaust phase of the combustion cycle. However, some of the combustion products enter into the engine crankcase during operation of the engine. Gases entering the crankcase are referred to as xe2x80x9cblow-byxe2x80x9d gases, in that the gases enter the crankcase as a result of having been blown by piston rings, valve guides of the engine and the like. Blow-by gases in the crankcase contain components deemed environmentally harmful, such as combustion by-products, including hydrocarbons and carbon monoxide, as well as oil mist produced in the crankcase and some water vapors. It is necessary to relieve the build-up of blow-by gases in the crankcase.
It is known in a naturally aspirated engine to discharge the blow-by gases from the crankcase to the intake manifold of the engine, for subsequent oxidation of the blow-by gases in the combustion process in the combustion cylinders. It is also known to simply discharge crankcase blow-by gases to the ambient environment, generally through a breather that separates at least a portion of any fluid droplets and/or particulate matter contained in the blow-by gases. Crankcase breathers typically have low filtration efficiency, thus allowing much of the unburned hydrocarbons, oil and fuel mist or soot particles to pass through the breather and be discharged into the ambient environment. Carbon monoxide contained in the blow-by gases will pass through a crankcase breather unabated.
In a pollution conscious society, contaminants contained in blow-by gases discharged to the environment cannot be ignored. Handling blow-by gases in a turbocharged engine provides unique difficulties, since returning the blow-by gases from the crankcase to the intake manifold requires use of an EGR pump, which is not yet commercially available. Returning blow-by gases to the intake side of a compressor in the turbocharger can result in fouling of the compressor wheel in a relatively short time period, thus causing loss of efficiency and subsequent turbocharger failure. The untreated blow-by gases also foul the aftercooler, causing loss of aftercooler effectiveness. This will lead to an increase in engine operating temperature, and cause the engine to fail.
U.S. Pat. No. 5,803,025 entitled xe2x80x9cBlow-by Disposable Systemxe2x80x9d describes a system in which blow-by gases from the crankcase are transported to an air-oil separator and to a pump. The pump transports the stream of contaminants into the exhaust system of the engine, where it becomes a portion of the overall exhaust emission stream.
The present invention is directed to overcoming one or more of the problems as set forth above.
In one aspect thereof, the present invention provides a blow-by filtration system for a crankcase of an internal combustion engine. A fluid conduit receives blow-by gases from the crankcase. A particle and droplet filter is disposed in the conduit, the filter adapted for removal of droplets and particles from a stream of blow-by gases flowing through the conduit. A catalyzed soot filter has an inlet receiving gases from the particle and droplet filter, and a primary heat exchanger is disposed in fluid flow communication between the particle and droplet filter and the catalyzed soot filter.
In another aspect thereof, the invention provides an internal combustion engine with a plurality of combustion cylinders, an intake manifold connected to the plurality of combustion cylinders, and an exhaust manifold connected to the plurality of combustion cylinders. A crankcase is associated with the plurality of combustion cylinders. A fluid conduit receives gaseous fluid flow from the crankcase. A particle and droplet filter is disposed in the fluid conduit. A primary heat exchanger is disposed in the conduit and has an inlet and an outlet, the primary heat exchanger inlet connected to receive fluid flow from the particle and droplet filter outlet. A catalyzed soot filter has an inlet and an outlet, the catalyzed soot filter inlet connected to receive fluid flow from the primary heat exchanger outlet.
In a further aspect thereof, the invention provides a method for treating blow-by gas in a crankcase of an internal combustion engine, with steps of filtering out at least some of any liquid droplet and particulate matter contained in the blow-by gases; passing the filtered blow-by gas through a primary heat exchanger; and passing the filtered blow-by gas from the primary heat exchanger through a catalyzed soot filter.